The instant invention is predicated upon the world's need for materials which possess a range of characteristics not present in naturally-occurring materials. Only through the synthetic engineering of uniquely propertied materials, can technological progress be freed from the constraints previously imposed by natural. With the constraints of nature's symmetry have been destroyed, the fabrication of materials having nonstoichiometric compositions, unique orbital configurations and variant bonding becomes possible.
The present invention provides for the fabrication synthetic materials which are particularly engineered to accomplish any desired task. In order to accomplish such an ambitious goal, it is necessary to introduce component species which have been preferentially incorporated in various conditions including excited species which can be individually inserted in special bonding configurations. The synthetically engineered electronic and chemical bonding configurations of those species in that host matrix are altered and permanently preserved. For example, completely novel non-equilibrium non-stoichiometric states can be frozen into a stable condition. It should be noted that the term "component" or "component material" as used herein refers to any species which participates in the interactions leading to the final synthetically engineered material, regardless of whether that species is physically present in the final product. Accordingly, components can include, inter-alia, inert gases or other species which transfer energy to, or otherwise influence the formation of the material.
Rapid quenching been described in the literature. By rapidly quenching precursor material from a non-solid state, certain non-equilibrium states and local bonding orders characteristic of the precursor material state can be preserved in the quenched state. In contrast thereto, the same precursor material, more slowly cooled from a non-solid to a solid state, will form a material which does not exhibit the non-equilibrium states and local bonding orders possible for the rapidly quenched material. Typically, the non-equilibrium material produced by rapid quenching will contain one or more phases characterized by disordered, amorphous, microcrystalline, nanocrystalline or polycrystalline structures.
Rapid quench techniques have heretofore been used to incorporate one or more "modifying" elements into the host matrix of a preselected material, thereby providing for the alteration of one or more of the physical, chemical, thermal, electrical or optical properties of that host material in a preselected manner. However, it was doubtful that said alteration could be accomplished without adversely affecting other properties which, in naturally occurring or unmodified materials, are seemingly interrelated to and dependent upon the altered properties. This principle will be referred to hereinafter as "modification". In other words, modification will be defined, for purposes of the instant invention, as the introduction of a modifying species into the host matrix of a precursor material for the purpose of uncoupling otherwise interrelated properties of that host matrix material. Modification will therefor affect at least the electronic configurations of the host matrix material so that physical and electronic transport properties of the material can be altered.
It is to be noted that various other methods are available by which modifying elements or species can be added to the host matrix of a precursor material. For instance, modified amorphous materials have heretofore been made by, e.g. thin film processes, chemical vapor deposition, sputtering and cosputtering, glow discharge, and microwave glow discharge. These methods of modification, the modified materials thereby obtained and the unique properties attained by modification are described in, for example, U.S. Pat. No. 4,177,473 to Stanford R. Ovshinsky for Amorphous Semiconductor Member and Method of Making the Same; U.S. Pat. No. 4,177,474 Stanford R. Ovshinsky for High Temperature Amorphous Semiconductor Member and Method of Making the Same; U.S. Pat. No. 4,178,415 to Stanford R. Ovshinsky and Krishna Sapru for Modified Amorphous Semiconductors and Method of Making the Same; and U.S. Pat. No. 4,520,039 to Stanford R. Ovshinsky for Compositionally Varied Materials and Methods for Synthesizing the Materials. Magnesium-based hydrogen storage alloys are described in U.S. patent application Ser. No. 08/259,793 filed Jun. 14, 1994 titled Electrochemical Hydrogen Storage Alloys and Batteries Fabricated From MG Containing Base Alloys. The disclosures of these patents are incorporated herein by reference.
The modified materials disclosed in the aforementioned patents are to be formed in a solid host matrix having structural configurations which have local rather than long range order. A modifier species may be added to the host matrix of the precursor material, said species having orbitals which interact with the orbitals of the host matrix resulting in the substantial modification of the electronic configurations of the host matrix of the precursor material. The atoms used for modification need not be restricted to "d band" or "f band" atoms, but can be any atom in which the controlled aspects of the interaction with the local environment and/or orbital overlap plays a significant role physically, electronically, or chemically so as to affect physical properties. The elements of these materials can offer a variety of bonding possibilities due to the multidirectionality of d-orbitals. For instance, in electrochemical electrode material, the multidirectionality ("porcupine effect") of d-orbitals provides for a tremendous increase in density and hence active storage sites.
Of particular interest relative to the instant invention is a disclosure which relates to the modification of the host matrix of precursor materials by a melt spinning process, said disclosure found in U.S. Pat. No. 4,339,255 to Stanford R. Ovshinsky and Richard A. Flasck for Method and Apparatus for Making a Modified Amorphous Glass Material, the disclosure of which is incorporated hereinto by reference. This '255 patent describes a method and apparatus for introducing a fluidic modifier into a host matrix, said fluidic modifier optionally containing one or more active gases, such as oxygen, nitrogen, silicon tetrafluoride, or arsine. The synthetic materials made by the disclosed process can be metallic, dielectric, or semiconductor modified amorphous glass materials. The modified synthetic materials can range from alloys, to materials with varying degrees of alloying and modification, to materials in which only modification and doping actions exist. While the '255 method provides for such modification species to be incorporated at various intervals or layers, at different rates and in different sequences; the number of species incorporated, the number and interval of layers and the rates and sequence of introduction are limited.
While the method disclosed in U.S. Pat. No. 4,339,255 permits the fabrication of modified ceramic materials, the process utilized to make the resultant material is that of melt spinning onto the peripheral surface of a chill wheel. As described hereinabove, melt spinning is a rapid quench process and can have quench rates as high as 108 degrees Centigrade per second. However, melt spinning is actually one of the slower rapid quench techniques, especially when compared to more rapid techniques such as sputtering. Therefore, it has heretofore not been possible to produce modified bulk materials at very high quench rates. It would, of course, be desirable (for production purposes, as well as for the fabrication of the highest quality modified materials) to fabricate modified bulk materials at very high quench rates, since the resultant materials would be characterized by a range of properties heretofore unobtainable.
Therefore, the instant invention relates to innovative fabrication techniques for the synthesis of novel classes of modified materials, which techniques do not suffer from any of the limitations imposed by the Flasck '255 process or other similar quench processes. More particularly, the instant invention includes the ability to simultaneously incorporate into a synthetically engineered material, metals or ceramics characterized by a very high melting point and other materials, such a magnesium, characterized by very high vapor pressure. Further, the instant invention provides for the modified element to be introduced, whether activated or not, at any point downstream of the crucible so as to control the degree and reactivity of its diffusion in the host matrix. Additionally, the melt spinning process used in the '255 patent permits only a rather limited rate of diffusion of the modifier species into the host matrix. Thus, it is not possible to use the method disclosed in that patent to fabricate a class of materials whose properties are purposely engineered on an atomic level.
In contrast to said heretofore developed rapid quench processes, the instant invention provides for the fabrication of synthetically engineered materials having a liquified host matrix into which energetic modifying elements are introduced. Due to the fact that the fabrication process of the instant invention may be repeatably cycled with a variety of host matrix precursors, successively deposited host matrix material may be repeatedly changed with the same modifier or sequentially changed with varying modifiers to develop either a multilayered, compositionally varied body of bulk material or a single homogenous body of bulk material which can be built to relatively thick dimensions. Because the process of the instant invention requires the interaction of the host matrix of the precursor material and the modifier material to occur during exposure to the atmosphere and while the modifier material is maintained in an activated state, both high quench rates and high diffusion rates are obtained. By incorporating the energetic modifier species into the host matrix at high diffusion rates in proper sequence, by specially controlled background environment, it becomes possible to fabricate a truly atomically alloyed synthetically engineered material, which material may include constituents of both high and low vapor pressure elements.
These and other objects and advantages of the instant invention will become clear from the drawings, the detailed description and the claims which follow.